Variations in the tide water level cause considerable problems in many ports, especially when Ro-Ro ships are involved. Even if the ship is provided with a communication ramp of its own, this cannot, alone, ensure uninterrupted traffic between the ship and the quay at all times.
It has been proposed to use a pontoon as an intermediary between the ship and the quay. The pontoon is provided with a ramp, whereby it is possible to distribute the difference in level between the ship and the quay upon two ramps.
The mooring of these pontoons is, however, difficult, and heeling movements at the pontoon cannot be fully avoided, when a heavy vehicle suddenly approaches, or leaves the pontoon.
The aim of the present invention is to propose a mobile caisson structure, which offers the same possibilities as a pontoon, concerning communication between the ship and the quay, but which is not liable to suffer from external actions of the kind making a pontoon unsuitable.